The present invention relates generally to electrical connectors and specifically to electrical connectors for terminating to conductors of a shielded cable.
In many applications, particularly in military and aerospace applications, shielded cable, such as cable in accordance with the M27500 cable specification, is used. Typically, the shielded cable includes not one but a plurality of conductive shields surrounding one or more conductors in the cable. Typically, a single shield surrounds at least one and no more than ten conductors. In some cases, an outer conductive shield will surround the plurality of conductive shields and shielded conductors. The shields protect the signals transmitted along the conductors from electromagnetic interference (EMI) due to electromagnetic radiation in the ambient atmosphere. The shields must be grounded to protect the conductors from EMI. Typically, the connector includes a conductive backshell that grounds the shields when the connector is plugged into a receptacle.
The ground to the backshell can be effectuated by a number of approaches. In one approach, one or more shields are soldered to a conductor which is connected to the backshell. The shields can be daisy chained together by soldering to utilize the same ground conductor. The daisy-chained shields and conductor are typically located inside of the backshell to protect them from EMI. As will be appreciated, exposing the daisy chained shields to electromagnetic radiation in the external environment can seriously compromise or degrade the EMI resistance of the shields. The EMI resistance is further weakened by the build up of electrical resistance from shield to shield along the daisy chain. The use of soldering and daisy chaining is not only labor intensive but also produces xe2x80x9cbrown crudxe2x80x9d contamination from the solder flux. The xe2x80x9cbrown crudxe2x80x9d is solder flux that wicks up underneath the jacket along the shield braid. Brown crud contamination is a type of corrosion that is unacceptable in many applications.
In other approaches, the shields are engaged with a clamping ring or coil spring and the ring or spring compressed between a metal seat and a tightened metal nut. Although the grounded portion of the conductive shields are well protected by the outer wall of the seat and the nut from exposure to electromagnetic interference, the nut often requires the shield to be cut to the proper length and properly positioned to permit the nut to be engaged properly with threads located on the outer wall of the seat. Otherwise, the shields could engage the threads and interfere with nut tightening and/or generate loose pieces or fragments of the conductive shield(s). In many applications, the shield must be temporarily clamped or otherwise held in position before the nut is tightened to effectuate the ground. Even when the shields are cut to the proper length, rotation of the ring or spring in the seat during rotation of the nut can cause the grounded shields to rub or abraid or otherwise frictionally contact against the seat, which can cause small fragments of the shield to be broken off. Such small fragments can later be dislodged, such as during the launch of a space vehicle, causing electrical shorts and vehicle malfunctions. The ability to remove such debris is hindered by the inaccessibility of the grounded shields after the nut is tightened. The grounded shields are generally not visible after nut tightening, complicating inspection of the integrity of the ground connection. The ground structure in such connectors is radiused, which provides a high profile for the connector, thereby creating problems where space is at a premium.
These and other needs are addressed by one or more embodiments of the present invention. Generally, the present invention provides a connector that utilizes a ground structure located inside of the backshell to provide ease of shield grounding.
In one embodiment, a connector for terminating a plurality of shielded conductors is provided that includes:
(a) a conductive backshell housing including a passage for receiving a plurality of conductors, the passage being disposed at a distal end of the conductive backshell housing;
(b) a connecting structure including a plurality of connecting elements for connecting to the corresponding plurality of conductors wherein each of a plurality of conductive shields surrounds one or more of the plurality of conductors, the plurality of connecting elements being disposed at a proximal end of the conductive backshell housing;
(c) one or more ground structures for grounding each of the plurality of conductive shields, each of the one or more ground structures being located inside the conductive backshell housing between the plurality of connecting elements and the passage; and
(d) a strain relief structure for restraining movement of the plurality of shielded conductors relative to the backshell housing.
The backshell housing can be composed of any conductive material and/or superconducting material and/or a composite of a conductive material and/or a superconducting material with a nonconducting material and/or a nonsuperconducting material. By way of example, the backshell housing can be composed of a plastic substrate with a metal coating. The backshell housing can be rectangular, circular, eliptical, or any other suitable cross-sectional shape and can be an integral or nonintegral (e.g., multipiece) assembly unit.
The connecting structure and connecting elements can be of any suitable configuration. Typically, the connecting structure has stacked rows of pin-type contacts.
The ground and strain relief structures can also be of any suitable configuration. For example, the structures can each include one or more movable clamping bars, jaws, or openings having smooth, serrated, ribbed, knurled, etc., configurations or edges that may be a part of or mounted on one or more parts of the backshell. In one configuration, the strain relief structure clamps the plurality of shielded conductors between a stationary bar (or a portion of the backshell) and a moveable bar and is located inside the backshell housing and near an opening of the passage. In one configuration, the ground structure clamps the conductive shield between a stationary bar (which is typically attached in some fashion to the backshell housing) and a surface of the conductive backshell housing (or another stationary bar).
In one configuration, the strain relief structure contacts an insulative cover enclosing the conductive shield and the plurality of shielded conductors. As will be appreciated, most shielded cables will have an insulated or dielectric (e.g., thermoplastic) cover. The cover is typically removed only as necessary to access the shields and the individual conductors, with the cover commonly being left in place where the cable contacts the strain relief structure.
The strain relief structure and ground structure can be located at any suitable location in the backshell. In one configuration, the strain relief structure is located between the ground structure and the distal end of the backshell housing. In another configuration, the ground structure is located between the ground structure and the distal end of the backshell housing.
The ground and strain relief structures can be formed by one or more integral or nonintegral components. In one configuration, the ground and/or strain relief structure includes a single unitary (or integral) bar for clamping or compressing a plurality of conductive shields or the cable, respectively. The bar (for either the ground and/or strain relief structure) may be moved or displaced by any suitable connector or connecting means such as one or more screws, a cam, a lever, a rivet, and a ratchet and locked or held in place by any suitable means such as one or more of a hook, a latch, a screw, a solder, a weld (e.g., a spot weld, an ultrasonic weld, etc.), a magnet, a rivet, an adhesive, and a lock washer. In another configuration, a plurality of ground structures is used, each of which includes a clamping bar, at least one end of which is secured to the conductive backshell housing, for electrically connecting at least a portion of the plurality of conductive shields with the conductive backshell housing. In the various configurations, rubbing, abrading, or other types of lateral movement of the shields is maintained at acceptable levels or substantially minimized.
The clamping bar in the ground and/or strain relief structures can be located in any suitable orientation relative to the backshell and/or another clamping bar. In one configuration, the clamping bar (of the ground and/or strain relief structures) is connected to the conductive backshell housing such that the bar moves in a direction that is at least substantially normal to at least a portion of a surface of the backshell housing to engage the plurality of shields but is at least substantially free of movement in a direction parallel to the surface. In one configuration, the bar moves in straight line motion relative to an adjacent surface of the backshell housing. In one configuration, the bar is at least substantially free of rotation (though the connectors connecting the bar to the backshell housing may rotate). In one configuration, the bar moves downwardly and upwardly relative to a ground surface of the backshell housing.
In another embodiment, a method for securing a plurality of shielded conductors to a connecting assembly is provided that includes the steps of:
(a) removing a portion of an insulating cover enclosing the plurality of conductors to provide access to a plurality of conductive shields enclosing the plurality of conductors;
(b) placing the plurality of conductively shielded conductors enclosed by the insulating cover into a strain relief structure in the connecting assembly;
(c) compressing the plurality of conductors in the strain relief structure to restrain movement of the plurality of conductors relative to a conductive backshell housing in the connecting assembly;
(d) engaging the accessible portions of the plurality of conductive shields with a ground structure in the connecting assembly, wherein at least a portion of the ground structure that contacts the plurality of conductive shields is at least substantially free of rotation in the engaging step (d); and
(e) connecting the plurality of shielded conductors to a plurality of connecting elements in the connecting assembly.
As will be appreciated, the engaging and compressing steps generally occur at different times. Typically, the compressing step will precede the engaging step to permit the strain relief structure to stabilize movement of the cable during the grounding operation.
In yet another embodiment, a connector for terminating a plurality of shielded conductors, includes:
(a) a conductive backshell housing including a passage for receiving a plurality of conductors, the passage being disposed at a distal end of the conductive backshell housing;
(b) a connecting structure including a plurality of connecting elements for connecting to the corresponding plurality of conductors wherein each of a plurality of conductive shields surround one or more of the plurality of conductors, the plurality of connecting elements being disposed at a proximal end of the conductive backshell housing;
(c) a strain relief structure for restraining movement of the plurality of shielded conductors relative to the backshell housing; and
(d) shield grounding means for clamping each of the plurality of conductive shields to a grounding surface of the conductive backshell housing. The shield grounding means is configured to maintain alignment with the grounding surface during engagement of the shield grounding means with the plurality of conductive shields. The shield grounding means can be any suitable clamping device, including without limitation one or more moveable or nonmoveable clamping bars or jaws, and/or a raised portion of the backshell housing that exerts a clamping force on the shields when the housing is assembled.
In one configuration, a grounding bar of the shield grounding means has freedom of movement in a direction at least substantially normal to the grounding surface of the backshell housing to engage the plurality of conductive shields and is at least substantially free of movement in a direction at least substantially parallel to the grounding surface.
In yet another embodiment, a method for grounding a plurality of shielded conductors is provided that includes the steps of:
(a) providing a plurality of conductive shields enclosing a plurality of conductors;
(b) passing the plurality of conductively shielded conductors through a passage in a backshell housing of a connecting assembly;
(c) engaging the plurality of conductively shielded conductors with a strain relief structure in the connecting assembly;
(d) after the passing step, engaging portions of the plurality of conductive shields with a ground structure in the connecting assembly; and
(e) connecting the plurality of shielded conductors to a plurality of connecting elements in the connecting assembly.
The various steps can include one or more substeps. For example, the engaging step (c) can include the step of compressing the plurality of conductors in the strain relief structure to restrain movement of the plurality of conductors relative to a conductive backshell housing in the connecting assembly. In one configuration, the engaging step (d) occurs interiorly of the passage.
The various embodiments can have one or more advantages relative to conventional devices. The grounded conductive shields can be externally accessible via a removable plate in the backshell housing. This permits the integrity of the grounding to be checked by quality control personnel, periodically during operation, and/or during routine maintenance functions. The accessibility further permits fragments or shards of the conductive shields to be removed by suitable techniques such as with an inert gas. The location of the grounding structure within the backshell can significantly enhance the EMI protection or resistance afforded by the shields. The moveable clamping member or bar can provide ease of use or installation and therefore significant labor savings. The shield does not have to be trimmed to any particular length for the ground to be realized. The ability to use shields of varying lengths provides labor savings and reduces (relative to existing designs) the generation of fines or shards from cutting of the shields. The moveable clamping member or bar can be secured by solderless techniques, thereby eliminating xe2x80x9cbrown crudxe2x80x9d and other types of solder-related contamination. The use of a clamping member or bar that has straight-line motion can prevent rubbing or abrading of the shields against the backshell or other clamping surface during clamping, thereby reducing, relative to conventional systems, the incidence of loose fragments or shards of conductive shield located in the backshell. This reduction further reduces, relative to conventional systems, malfunctions (e.g., electrical short circuits) attributable to such fragments, thereby increasing system reliability. The backshell can have a low profile (a height that is typically no more than about 0.060 inches greater than the maximum face height of the connector), which permits more connectors to be located or stacked in a given space. This small size can be especially important in applications where space is at a premium. The strain relief and ground structures can be located at discrete or spaced apart locations. The use of the same structure to perform both functions is poor practice and can lead to a loss of system integrity.
The foregoing summary is intended to be neither exhaustive nor complete. As will be appreciated by one of ordinary skill in the art, the above-noted features may be used alone or in combination to form other embodiments of the invention. Such other embodiments are considered to be a part of the invention(s) set forth and/or claimed herein.